1. Is there anyway we can measure time without depending on or using light? If we can, what are they and do special relativistic effects still take place in "close to c" relative velocity situations by using this method of time keeping? 2. My second question relates to relative movement. Time dilation suggests that the time measured in two different reference frames moving with a relative velocity to each other is different. This conclusion then suggests that the time measured in a moving reference frame relative to a stationary one is less than the time measured by the stationary observer for the moving reference frame. Because both frames are moving relative to each other, doesn't the reference frame which we originally dictate to be the one moving see that time actually slows down in the reference frame that we considered to be stationary? This is because the velocity that we assumed one reference frame had relative to another can be applied to the other reference frame in the opposite direction. Therefore, we can assume both reference frames believe the other reference frame has a slower passage of time. If what I said so far is true, then at any instant the amount of time that has passed for each observer in their own reference frame is the same and each observer believes less time has passed in the other reference frame. (This contradiction relates to the twin paradox, without the acceleration part that many use as a "solution" to the paradox.) Now I want to know, is what I have said a paradox? If it is, what does this suggest? One thing it can suggest is that the way we measure time is flawed. But what else can be said about the nature of time?